1. Field of the Invention
The present invention relates to a solid-state imaging device having a penetration electrode formed in a semiconductor substrate, for example, a camera module.
2. Description of the Related Art
In recent years, miniaturization of various electronic appliances has progressed, and a solid-state imaging device having a semiconductor image sensor is also required to be miniaturized. As one technique to realize the miniaturization, there is a penetration electrode in which a through-hole is formed to extend from a rear surface side of a semiconductor chip on which a semiconductor image sensor is formed to an internal electrode on a front surface side so as to electrically connect an electrode on the rear surface side to the internal electrode on the front surface side through a conductor layer buried in the through-hole.
A conventional method of forming a penetration electrode has the following structure, for example. A through-hole is formed to extend from a rear surface side of a silicon substrate to a front surface side. Thereafter, an insulating film is formed in the through-hole. After the through-hole is extended to the insulating film and an insulating interlayer which are present between a bottom surface of the through-hole and an internal electrode, a conductor layer (penetration electrode) is buried in the through-hole (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2007-53149).
However, when the through-hole is formed in the insulating interlayer, a small-size through-hole having a diameter ranging from about 20 to 30 μm is formed. For this reason, a resist film thickness must be made large, and the manufacturing cost increases because a long developing time is required to pattern the resist. The insulating film formed on the silicon substrate in the through-hole is damaged by plasma asher used in removal of the resist, and a short circuit occurs between the silicon substrate and the conductor layer.